Various lasers have been actively developed, and in particular, among the lasers, a laser with high output and high spatial coherence has been demanded. As a method for realizing this, there is known a method which realizes high output by coherent addition (coupling) of outputs of a plurality of lasers. As an example, coherent addition (coupling) of lasers by means of evanescent coupling of laser arrays or diffraction coupling by using a Talbot mirror have been studied. An example of the evanescent coupling is disclosed in “Diode Laser Arrays,” D. Botez and D. R. Scifres, Cambridge Studies in Modern Optics, 1994, p. 1, and an example of the Talbot resonator relating to solid-state lasers is disclosed in “A Coherent All-Solid-State Laser Array Using the Talbot Effect in a Three-Mirror Cavity,” Y. Kono, M. Takeoka, K. Uto, A. Uchida, and F. Kannari, IEEE Journal of Quantum Electronics, Vol. 36, 2000, pp. 1-8, and an example of the Talbot resonator relating to laser diode arrays is disclosed in “Phase-locking of the 2D structures,” V. V. Apollonov, S. I. Derzhavin, V. I. Kislov, V. V. Kuzminov, D. A. Mashkovsky, and A. M. Prokhorov, Opt. Express 4, 1999, pp. 19-26.